The present invention refers to a device for shifting a tensioning roller for tensioning a belt.
In one known device for shifting a tensioning roller, a tensioning roller is normally arranged eccentrically on a base plate. That base plate, in its turn, is fastened in pivotable and lockable manner on a housing In such an embodiment, the tensioning roller is shifted by pivoting the base plate on the housing. Its position is fixed by bolting the base plate to the housing. In the event of different heating of individual parts which may result in their different expansions, changes in the tension of the belt then result in operation. Belt tension changes are undesirable, particularly in the case of a drive in which no slippage or skipping of a belt tooth may take place. On the other hand, too high tensioning of the belt should also not occur, as this would lead to its impermissible belt heating and destruction. As shown, for example, in European Published Application No. 150 893, it is therefore customary to have an adjustable bolt and a spring act upon the base plate. Such measures are, however, expensive and complicated. Furthermore, even this does not produce a belt tension which is adapted to the prevailing operating and expansion conditions. If only a spring is used, then impermissible oscillations of the belt result. For this reason, hydraulically settable and adjustable devices are proposed in European Published Application No. 212 119. However, they are even more complicated and furthermore require means which produce and regulate the hydraulic pressure.